Remove unused features.

Author: nnethercote

compiler/rustc_query_system/src/lib.rs

@@ -2,9 +2,7 @@
 #![feature(core_intrinsics)]
 #![feature(hash_raw_entry)]
 #![feature(min_specialization)]
-#![feature(extern_types)]
 #![feature(let_chains)]
-#![feature(inline_const)]
 #![allow(rustc::potential_query_instability)]
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]